Pneumatically actuated stapling or driving tool for fastening means

ABSTRACT

IN A PNEUMATICALLY ACTUATED STAPLING DEVICE IN WHICH THE AIR DISPLACED BY THE PISTON DURING ITS DRIVING STROKE IS STORED IN AN ADJOINING CHAMBER OF THE WORKING CYLINDER, THE AIR PRESSURE IN SAID CHAMBER IS INCREASED BY ADDITIONAL COMPRESSED AIR FROM THE INTERIOR OF THE CYLINDER, WHICH AIR IS ADMITTED TO THE CHAMBER AT THE END OF SAID DRIVING STROKE. THE AIR PRESSURE IN THE ADJOINING CHAMBER IS LIMITED BY AN ADJUSTABLE PRESSURE RESPONSIVE VALVE, WHICH CONTROLS THE ADMISSION OF ADDITIONAL COMPRESSED AIR TO SAID CHAMBER AT THE END OF THE DRIVING STROKE.

Sept. 20, 1971 BQLTE PNEUMATICALLY ACTUATED STAPLING' 0R DRIVING TOOL FOR FASTENING MEANS Filed Sept. 30, 1969 3 Sheets-Sheet z l l 1 1 a i l 2 l 0 MM 5: 6 l lfmu l1 9 M a i L V Sept. 20, 1971 3,605,560

A. BOLTE PNEUMATICALLY ACTUATED STAPLING 0R DRIVING TOOL FOR FASTENING MEANS Filed Sept. 30, 1969 3 Sheets-Sheet 3 United States Patent 1 3,605,560 Patented Sept. 20, 1971 3,605,560 PNEUMATICALLY ACTUATED STAPLING OR DRIVING TOOL FOR FASTENING MEANS Adolf Bolte, 34 Boehmerstrasse, Hannover, Germany Filed Sept. 30, 1969, Ser. No. 862,356 Claims priority, application Germany, Oct. 4, 1968, P 18 01 163.7 Int. Cl. FlSb /22, 11/15, 13/042 US. Cl. 91-399 6 Claims ABSTRACT OF THE DISCLOSURE DESCRIPTION This invention relates to a pneumatically actuated stapling device for driving fasteners such as nails, pins, clamps, staples, dowels, etc. into a work piece and more particularly to an improved stapling device, wherein air is stored in an adjoining chamber of a working cylinder for returning a driving piston to its initial position. This air is displaced by said piston during its working stroke and is admitted to said adjoining chamber. The pressure of this air is increased by the admission of compressed air from the working cylinder towards the end of the working stroke of the piston.

In a conventional pneumatic stapling device the additional compressed air towards the end of the working stroke of the piston is admitted to the adjoining chamber via a port at the lower portion of the working cylinder. As soon as the piston during its working stroke passes said port the upper portion of the working cylinder communicates with the adjoining chamber and compressed air flows from the cylinder into the adjoining chamber. This port is provided with a check or backpressure valve preventing the back-flow of air to the working cylinder when the upper face of the piston is no longer under air pressure but permitting the air from said adjoining chamber to flow underneath the piston and to move same back to its initial retracted position. Pressure reduction at the upper face of the piston occurs after the piston has reached its lowest final position, allowing the air contained in the adjoining chamber to force the piston back to its initial position.

In practice after every [working stroke of the piston a somewhat larger quantity of air than required for moving the piston back into its initial position is stored in the adjoining chamber. Therefore during the operation of the device the adjoining chamber is filled with air under higher pressure than necessary. This excess air pressure retards the working stroke of the piston and the working speed of the piston and the efiiciency of the device are reduced.

It is accordingly a main object of the invention to provide a pneumatic stapling device of the forementioned structure, which enables very high working speeds of the piston. Another object of the invention is the provision of an adjustable pressure responsive valve means which prevents an excessive rise of pressure in the adjoining chamber, whereby the speed of operation and the efiiciency of the stapling device are increased.

Still another object of the invention is to provide a novel and improved fastener driving implement of relative light weight so that it is easy to handle and use as a portable tool.

A stapling device constructed in accordance with the invention includes a pressure limiting valve arranged between the external wall of the adjoining chamber and the working cylinder and controlling the admission of compressed air to said chamber. This valve closes and opens automatically and is equipped with a valve housing including a sleeve or bushing having an intermediate partition base or forming a valve disk seat and an internal threading at its outer end for receiving an adjusting screw. Said screw regulates the tension of spring means which acts on a valve disk which, in turn, is adjacent a shoulder in the valve housing. Said valve disk is mounted on a backing plate via a valve stem connection. Between the seat of the valve disk and the shoulder in said intermediate base or partition wall air ports are arranged for communicating with the adjoining chamber. The valve housing is appropriately disposed between a wall of the working cylinder and the casing of the stapling device. The pressure limiting valve according to the invention blocks the admission of compressed air into the adjoining chamber when a predetermined pressure limit is exceeded in said adjoining chamber such that even at a rapid firing rate development of excess pressure in the adjoining chamber is obviated and the working stroke of the driving piston is not braked or retarded by the resistance of additional air having to be displaced by the piston. In this way the piston maintains its impact power.

Other features, objects and advantages of the invention will be seen from the accompanying drawings, which represent by way of example a preferred embodiment of the invention.

In the drawings:

FIG. 1 is a fragmentary sectional view of the stapling device embodying this invention showing a piston in the initial position;

FIG. 2 represents the device of FIG. 1 with the piston at the end of its working stroke and FIG. 3 shows a fragmentary sectional view on an enlarged scale of a pressure limiting valve.

The device shown in FIGS. 1 and 2. is a portable pneumatically actuated implement for driving staples, nails and other fastening means into a work piece. The device comprises a casing 1 with a working cylinder 2, an adjoining chamber 3, and a working piston 4 equipped with a fastener driving blade or driver 5. Several open ports 6 in the lower end of the side wall of working cylinder 2 communicate with the adjoining chamber 3. In the lower portion of said side Wall but above the ports 6 and below the upper end of the cylinder 2 an additional port 7 is located which also connects the adjoining chamber 3 with the interior of the working cylinder 2. Said port 7 is controlled by a pressure limiting valve 8. In the lower end of working cylinder 2 is mounted an elastic bumper 9 which limits the driving stroke of piston 4. As it is best seen from FIG. 3 the pressure limiting valve 8 comprises a housing 10 in the form of a bushing which, at its internal end adjacent the side wall of working cylinder 2, is provided with a partition wall 11 having a central aperture. Said aperture is closed by a valve disk 12 which contacts said partition Wall 11. At its outer or external end the valve housing 10 is provided with an internal thread 13 receiving an adjusting means or screw 14 which can be turned or actuated from the outside. Adjacent the partition wall 11 a shoulder 15 is located which is contacted by a backing plate 16 having an elastic sealing ring 19 engaging the housing 10'. Between said backing plate 16 and the adjusting screw 14 a compression spring 17 is mounted. The spring tends to press the backing plate 16 against the shoulder 15. The valve disk 12 is mounted on a valve stem 18 of a cylindrical shape which is connected to the backing plate 16. Orifices 20 for admitting compressed air from the working cylinder 2 into the adjoining chamber 3 via the port 7 are provided between the partition wall 11 and the shoulder 15. The air contained in the lower portion of working cylinder 2 is moved by piston 4 during its staple driving stroke and via the ports 6 is forced into the adjoining chamber 3. Part of this air also flows via port 7 and opened pressure limiting valve 8 into said chamber 3. As soon as piston 4 has reached port 7 compressed air from the working cylinder 2 above piston 4 flows through port 7 and the opened pressure limiting valve 8 whereby the air pressure in the adjoining chamber 3 is increased. When this pressure in the adjoining chamber 3 exceeds the predetermined tension of the spring 17, which can be adjusted and controlled by way of the adjusting screw 14, the backing plate 16 is moved against the spring 17 towards the adjusting screw 14, whereby the valve disk 12 is pressed onto the partition wall 11 and closes its aperture. The admission of further compressed air into the adjoining chamber 3 is thereby blocked. When the air pressure in the adjoining chamber 3 has decreased, the force of spring 17 again causes valve 8 to open.

In order to rapidly obtain the desire pressure level particularly with pneumatical stapling devices of larger air volume it would be appropriate to locate several pressure limiting valves at the circumference of the working cylinder. Likewise, it is advantageous, as becomes apparent from the drawings, to arrange the pressure limiting valve in such a way that its adjusting screw can be operated from the outside.

Various changes and modifications may be made in this invention without departing from the scope and spirit thereof. Accordingly, no limitations are intended except insofar as set forth in the claims which follow.

What I claim is:

1. In a pneumatically actuated fastener driving device including a casing having a cylinder therein, means for admitting air under pressure from a source of compressed air to said cylinder, a piston movable in said cylinder, an adjoining chamber for receiving air displaced by said piston from said cylinder, and means for admitting compressed air from said cylinder into said chamber at the end of the working stroke of said piston; the improvement comprising at least one valve means for controlling the admission of compressed air from said cylinder to said adjoining chamber and for limiting the air pressure therein, said valve means including a valve housing with a shoulder formed therein, a partition wall with an aperture therein providing a valve seat, and a threaded end, an adjusting screw threadedly engaging said end of said housing, a backing plate sliding in said housing, and a spring located between said adjusting screw and said backing plate and biasing said backing plate toward said shoulder.

2. The device as in claim 1, wherein said valve means further comprises a valve stem connected to said backing plate and a valve disk carried on said stem, and wherein air outlet ports are located in said housing between said shoulder and said partition wall and lead into said adjoining chamber.

3. The device as in claim 1, wherein said valve housing is secured between said cylinder and said casing of the device.

4. The device as in claim 1, wherein said adjusting screw is operable from the outside of said casing.

5. In a pneumatically actuated fastener driving device including a casing having a cylinder therein, means for admitting air under pressure from a source of compressed air to said cylinder, a piston movable in said cylinder, an adjoining chamber for receiving air displaced from said cylinder by said piston during its working stroke, and port means in said cylinder for admitting compressed air from said cylinder into said chamber at theend of the working stroke of said piston; the improvement comprising adjustable pressure responsive valve means in said adjoining chamber controlling the admission of compressed air from said cylinder to said adjoining chamber and limiting the air pressure therein.

6. The device as in claim 8, wherein said valve means comprises a valve member for closing said port means when the pressure in said chamber exceeds a predetermined level, biasing means engaging said valve member and biasing said valve member to normally open said port means, and adjusting means engaging said biasing means, said adjusting means being operable from the outside of said casing of said device.

References Cited UNITED STATES PATENTS 1,494,030 5/ 1924 Slater 9-1399 2,807,081 9/1957 Black 91-399 2,983,922 5/1961 Juilfs 91399 PAUL E. MASLOUSKY, Primary Examiner U.S. Cl. X.R. 91-468- 

